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KERNEL HARDNESS OF WILD RICE AS AFFECTED BY DRYING AIR TEMPERATURE AND MOISTURE GRADIENT
Author(s) -
WIRAKARTAKUSUMAH M. A.,
LUND D. B.
Publication year - 1978
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1978.tb02312.x
Subject(s) - moisture , relative humidity , humidity , degree (music) , water content , starch , temperature gradient , starch gelatinization , chemistry , air temperature , yield (engineering) , agronomy , horticulture , materials science , composite material , food science , meteorology , biology , physics , geotechnical engineering , acoustics , engineering
Samples of wild rice (38‐40% moisture, wet basis) were dried to 7‐8% moisture using three different drying air temperatures and relative humidities, namely, 110°C‐63% relative humidity, 110°C‐6% relative humidity, and 60°C‐20% relative humidity. Samples were subsequently hulled immediately (hulled hot) or hulled after storing 24 hr at room temperature (hulled cold). Evaluations included determination of hulling efficiency, kernel hardness and degree of gelatinization. Hulling was most efficient when a high drying air temperature was used and when the kernels were hulled immediately after drying. Total yield was not affected by temperature gradient or moisture gradient which the wild rice kernels experienced during drying. Head yield was maximum when wild rice was dried under conditions of a high drying air temperature and low mositure gradient, and when it was hulled hot, immediately after drying. The kernel hardness test confirmed that kernels were harder when dried under high temperature, low moisture gradient conditions. Degree of gelatinization studies confirmed that about 90‐95% of the starch in kernels dried under these conditions was gelatinized. The gelatinization of starch was influenced by both temperature and rate of drying. Susceptibility of kernels to cracking increased with increasing magnitude of moisture gradient within kernels. The best processing conditions for wild rice using criteria previously described consist of drying under high air temperature and a low moisture gradient, and hulling the kernels hot, immediately after drying.